Airbag Device

ABSTRACT

There is provided an airbag device being excellent in performance of protection of an occupant wherein a folded airbag ( 10 ) undergoes sequential and orderly expansion starting from a region where the expansion ought to be started. It is characterized in that a gas rectification member ( 12′ ) for rectifying and guiding a gas generated from an inflator ( 30 ) up to the vicinity of a part of the airbag ( 10 ), inflating in the initial expansion thereof, is provided substantially at the central part of the airbag ( 10 ).

TECHNICAL FIELD

The invention relates to an airbag device of an automobile.

BACKGROUND TECHNOLOGY

An airbag device is installed on the central part of a steering device50P, for example, as shown in FIG. 16, and a member 40P for display isprovided on the central part of the airbag device, and on the outercircumference thereof ,an airbag cover 16P is provided, havingtear-lines on the back side that can be split and torn into a pluralityof cover pieces 16Pb when the airbag 16P undergoes inflation andexpansion, containing the folded airbag and an inflator therein (seePatent Document 1).

FIG. 17 and FIG. 18 are sectional views showing another airbag deviceprovided with the same structure as that shown in FIG. 16. A diffuser32R provided with gas exhaust holes 30Ra for exhausting gas is disposedon an inflator 30R of this airbag device, and an inflator attachmentopening of an airbag 10R is secured to a position denoted by Q, while atether belt 11Ra for constraining an extension length of the airbag 10Ris provided on the central part of the airbag 10R, and the end of thetether belt 11Ra is secured by a fixture member provided on the head ofthe inflator.

As is evident from FIG. 17, the diffuser 32R provided with a pluralityof gas exhaust holes 32Ra is disposed between the inflator 30R and thefolded and contained airbag 10R. At the time of actuation of theinflator 30R, a gas generated from the inflator 30R passes through thegas exhaust holes 32Ra and applies a gas pressure directly to thecentral part of the folded and contained airbag 10R (see Patent Document2).

With the structure of this airbag device, the gas pressure isconcentrated in the central part of the folded airbag 10R at the time ofactuation of the inflator 30R so that a state of the folded airbag 10Ris collapsed and the airbag portion above the gas exhaust holes 32Ra ispushed out exponentially in the direction of expansion of the airbag, tothereby enable a tear-line 16Ra provided on the back side of the airbagcover 16R to be ruptured, causing the airbag portions to burst outlargely toward a driver seat.

Due to an inertia force of the airbag portions as burst out, a remainingportion of the airbag bursts out at once toward the driver seat. Thisbursting-out is said to be as “a punching phenomenon” and there is apossibility that the maximum bursting-out velocity reaches 300 km/h,thereby inflicting harm on an occupant. According to the inventiondisclosed in Patent Document 2, it seems that an opening of the airbagcover 16R for expansion of the airbag 10R at the time of rupture of theairbag cover 16R is rendered small as a countermeasure against such apunching phenomenon so that the airbag 10R is not burst out at once,resulting in reducing damage caused by the punching phenomenon. However,if the opening is rendered small, when the folded and contained airbag10R is pushed out at once toward the opening, the airbag 10R is cloggedat the opening of the airbag cover so that the airbag portion positionedin the vicinity of the opening is difficult to protrude toward thedriver seat due to a gas pressure to be applied from behind.

In this state, since the airbag 10R is difficult to protrude, there is apossibility that the gas pressure inside the airbag 10R furtherincreases and the airbag cover 16R itself undergoes inflation, so thatthe airbag cover 16R increases the inflation velocity while forciblyexpanding its opening so that the airbag 10R bursts out through theopening of the airbag cover 16R. In addition to that, in cases whereonly the portion which is slipped out of the opening in the initialstage of expansion of the airbag 10R first busts out to undergoinflation and expansion partially, the direction of expansion of theairbag is changed in whole to cause the direction of expansion unstable,thereby deteriorating performance of the airbag device to protect theoccupant.

Next, there is described still another conventional airbag device. FIG.19 is a traverse sectional view of this airbag device. As shown in thefigure, an airbag 10L is folded and contained between an airbag cover16L and an inflator 30L. A tear-line 16La in the shape substantiallyresembling the letter H is provided on the back side of a front facewall of the airbag cover 16L, and an inflator attachment opening of theairbag 10L is secured to a flange 30Lb provided on the outercircumference of the inflator 30L (see Patent Document 3).

According to this airbag device, a gas pressure is concentrated in thewhole back portion of the folded airbag 10L at the time of actuation ofthe inflator 30L, and concurrently the lump of the airbag 10L above thegas exhaust holes 30La is pushed out exponentially in the direction ofexpansion of the airbag, to thereby enable the tear-line 16La in theshape substantially resembling the letter H provided on the back side ofthe airbag cover 16La to be ruptured so that these airbag portionslargely burst out toward the driver seat. Although it is possible tocontrol a quick bursting-out of the airbag in a specific folding manner,it requires a folding manner wherein the airbag is normally difficult toundergoes expansion in order to control a quick bursting-out of theairbag, causing a problem in that expansion time until the airbag isfully expanded is delayed. On the other hand, if the airbag is foldednot to delay the expansion time, there occurs a punching phenomenondescribed as above.

FIG. 20 is a view showing each state of inflation of the airbag withrespect to time elapsed from the initial expansion of the airbag of aconventional airbag device. A dummy is postured in a seating positionclose to the airbag (this seating position is said to be out of normalseating position i.e. Out of Position, hereinafter referred to as “OOPstate”). The airbag is formed in the shape of a bag that is expandableinto a flat spherical shape (an ellipsoidal shape) by preparing astitched part P by stitching respective outer circumferential edges oftwo pieces of cloth substantially circular in shape. Accordingly, thestitched part P is positioned in the center of the side face of the flatspherical airbag at the time of completion of expansion.

As shown in FIG. 20A to 20D, when the airbag undergoes inflation in themanner that the stitched part P thereof rests against the neck of thedummy, the portion of the airbag rested against the neck of the dummy iscontrolled in inflation immediately before the airbag is completelyinflated, so that the controlled portion, particularly the portion thatbecomes maximum in airbag diameter, undergoes inflation exponentially inthe completion stage of inflation of the airbag, leading to thepossibility of inflicting harm on the neck. A phenomenon which occurswhen the gas generated from the inflator increases the inner pressure ofthe airbag exponentially just before or at a moment of the completion ofinflation (a phenomenon in which an occupant is repelled by the airbagwhich is caused by the increase of the inner pressure of the airbagexponentially from a loosened state) is said to be a so-called “amembrane phenomenon”.

Meanwhile, as the method of folding the airbag, there are known (1) amethod of folding like bellows the airbag, (2) a method of folding theairbag in the shape of a roll, (3) a method of folding like bellows theairbag in the direction of extension of the airbag sterically (disclosedin Patent Document 2), and so forth. Although Patent Document 3 does notdisclose with which method the airbag is folded, the punching phenomenonwill occur in any folding method except the specific folding mannerdisclosed as above. However, there was no specific means to preventoccurrence of the membrane phenomenon in the OOP state disclosed asabove except the regulation of opening manner of the airbag cover.

-   -   Patent Document 1: U.S. Pat. No. 6,739,620-B1    -   Patent Document 2: US-2001/42978-A1    -   Patent Document 3: JP-3-38254-U

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

It is an object of the invention to provide an airbag device capable ofpreventing occurrence of a punching phenomenon even in an folded andcontained airbag regardless of its methods of folding, and of reducingdamage inflicted on an occupant even in an OOP state, the airbag devicebeing excellent in performance of protection of an occupant even in anormal expansion of the airbag and also provide an airbag device whichis simple in structure and low cost and being usable as an airbag devicefor an occupant seat such as a driver seat and a front passenger seat,being capable of smoothly expanding the airbag with relatively lowpressure and of reducing a pressure loss without reinforcing a strengthof each member such as a housing, a cover and so forth more thanrequired.

Means for Solving the Problem

To achieve the above object, the invention disclosed in claim 1 is anairbag device comprising, an inflator, an airbag communicating with theinflator for undergoing inflation by a gas generated from the inflator;and a holding member for holding the airbag in a state as folded andcontained therein, and pressing down the outer circumferential side ofthe airbag, to thereby restrain inflation and expansion of the airbag inthe direction of the side thereof, caused by the gas generated from theinflator at least in the initial expansion of the airbag, wherein a gasrectification member for rectifying and guiding the gas generated fromthe inflator up to the vicinity of a part of the airbag, inflating inthe initial expansion thereof, is provided substantially at the centralpart of the airbag, wherein the holding member has an opening facing tothe part of the airbag that will be inflated in the initial expansionthereof, and the airbag undergoes inflation and expansion through theopening.

The invention disclosed in claim 2 is the airbag device disclosed inclaim 1 characterized in that the airbag is folded and contained on aside of the outer circumference of the gas rectification member.

The invention disclosed in claim 3 is the airbag device disclosed inclaim 1 or 2 characterized in that the gas rectification member istubular in shape, the airbag is provided with a communicating port forcommunicating with the inflator, and the gas rectification member isextended from a peripheral edge of the communicating port up to thevicinity of the part of the airbag that will inflate in the initialexpansion thereof.

The invention disclosed in claim 4 is the airbag device disclosed in anyof claims 1 to 3 characterized in that the gas rectification member ismade of a woven cloth.

The invention disclosed in claim 5 is the airbag device disclosed in anyof claims 1 to 4 characterized in that the gas rectification member isdisposed as a member having a function for protecting the airbag fromheat of the inflator and impactive pressure thereof.

The invention disclosed in claim 6 is the airbag device disclosed in anyof claims 1 to 5 characterized in that the holding member is made of awoven cloth for containing the airbag covered thereby.

The invention disclosed in claim 7 is the airbag device disclosed in anyof claims 1 to 6 characterized in that the holding member is containedin an airbag cover.

The invention disclosed in claim 8 is the airbag device disclosed inclaim 7 characterized in that tear-lines to be split and torn upongeneration of the gas in the inflator to thereby form an expansion portof the airbag are provided on a back side of the airbag cover.

The invention disclosed in claim 9 is the airbag device disclosed in anyof claims 1 to 8 characterized in that a tether belt for restraining anextension length of the airbag, toward an occupant side, is disposed inthe airbag.

Effect of the Invention

When the airbag 10 undergoes expansion, flow of the gas generated fromthe inflators is rectified by the gas rectification member, to be guidedup to the vicinity of the part of the airbag that will inflate in theinitial expansion thereof, and concurrently, the holding member controlsinflation of the airbag in the direction of the side face thereof andapplies resistance through the opening, so that the airbag undergoessequential and orderly expansion starting from a region thereof, to beexpanded from the first, thereby preventing a punching phenomenonwhereby the airbag partially bursts out in a lump toward the occupantside.

Since the gas rectification member compresses the folded airbag betweenitself and the holding member by the agency of the gas pressure in theinflator by disposing the folded airbag on the outer circumference ofthe gas rectification member, the folded and contained airbag can befirmly maintained so that the folded airbag collapses smoothly due tothe impact given in the initial expansion thereof, thereby preventingoccurrence of the punching phenomenon whereby the airbag partiallybursts out in a lump toward the occupant side with success.

Further, since the airbag device has a structure in which a forceapplied to the gas rectification member can be fended off with theairbag so that the gas rectification member no longer requires aparticular strength, while since the protective member for protection ofthe periphery of the inflator communicating port can be used as therectification member, the protective member originally intended forprotection of only the peripheral portion of the inflator communicatingport can carry out a function as a protective member for protection ofthe whole inner face of the airbag. Still further, the protective memberspreads from the periphery of the inflator communicating port toward theouter circumference of the concentric circle from the first, when theprotective member is disposed on the inner circumference side of thefolded airbag, the protective member is actually multiple-folded tothereby form pleats, so that with just one sheet of the protectivemember, it is possible to obtain the same protection effect as isobtained with several sheets of the protective member, thereby veryefficiently protecting the airbag in whole.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front elevation showing an airbag device fitted to asteering wheel;

FIG. 2 is a traverse cross-sectional view of the airbag device, taken onarrow I-I of FIG. 1;

FIG. 3 is a perspective view showing a back side of a base plate;

FIG. 4 is a perspective view of a connecting member;

FIG. 5A is a front elevation of a cushion ring shown in FIG. 2 whileFIG. 5B is a side view showing a part thereof, in section;

FIG. 6A is a see-through perspective view showing the interior of aninflated airbag while FIG. 6B is a perspective view showing theuninflated airbag;

FIGS. 7A to 7H each is a schematic view showing an operating procedurefor folding the airbag with the use of an airbag-folding machine;

FIG. 8A is an expansion view of a holding member prior to covering theairbag, FIG. 8B is a perspective view showing the back side of thefolded airbag, FIG. 8C is a perspective view showing the airbag coveredwith the holding member, and FIG. 8D is a backside view of the airbagcovered with the holding member;

FIG. 9A is a perspective view of an airbag cover, while FIG. 9B is aback side view of the airbag cover;

FIG. 10 is a view showing respective cover pieces in as opened-up state,as seen from an occupant side;

FIG. 11 is a view showing an expansion action of the airbag device M1;

FIG. 12 is a view showing an expansion state of the airbag device M1according to the first embodiment;

FIG. 13 is a cross sectional view showing an airbag device M2 for afront passenger seat according to a second embodiment of the invention;

FIG. 14 is an enlarged view showing a clamped-secured state of a gasrectification member, an airbag and a holding member;

FIG. 15 is a schematic enlarged longitudinal sectional view of anotherairbag device M3 for the front passenger seat;

FIG. 16 is a sectional view showing a conventional airbag;

FIG. 17 is a view of showing an expanded conventional airbag;

FIG. 18 is a view showing a state of containing of the conventionalairbag;

FIG. 19 is a view showing another contained conventional airbag; and

FIG. 20 shows a view showing each state of inflation of the airbag withrespect to time elapsed from the initial stage of the expansion of theairbag of a conventional airbag device.

EXPLANATION OF REFERENCE NUMERALS

10 a . . . airbag main body, 11 a . . . tubular tether belt, 12 . . .protective member, 12′ . . . gas rectification member, 14 . . . holdingmember, 16 . . . airbag cover, 20 . . . linkage member, 22 . . . cushionring, 24 . . . base plate, 30 . . . inflator

BEST MODE FOR CARRYING OUT THE INVENTION

There is described hereinafter an airbag device M1 for a driver seataccording to a first embodiment of the invention, with reference to theaccompanying drawings. FIG. 1 is a front elevation showing the airbagdevice M1 is fitted into a steering wheel, and FIG. 2 is across-sectional view thereof taken on arrow I-I of FIG. 1. As shown inFIGS. 1, and 2, the airbag device M1 is assembled into the central partof a steering wheel of a vehicle and comprises a decorative member 40,an airbag 10 and an airbag cover 16. For convenience's sake, a side ofthe decorative member 40 on the side of an occupant is referred to as afront side while a side thereof opposite from the front side is referredto as a back side in the present specification.

As shown in FIG. 2, the airbag 10 comprises an airbag main body 10 a anda tubular tether belt 11 a for restricting an extension length of theairbag main body 10 a, and the airbag 10 folded like bellows toward theoccupant side is contained within the airbag cover 16.

The airbag 10 is covered with a holding member 14 in such a way as topress down a side face of the airbag 10 on the outer circumferencethereof, to thereby restrain inflation and expansion of the airbag 10 inthe direction of the side face thereof. The main body 10 a and theholding member 14 are secured to a base plate 24 by a cushion ring 22inserted into the airbag 10. Further, the airbag cover 16 is secured tothe base plate 24 in such a way as to cover up airbag 10 and such.

Meanwhile, an attachment bolt 40 a positioned on the back side of adepressed part 16 a formed on the airbag cover 16 on the side of theoccupant and protruding toward the back side of the decorative member 40is secured to a connecting member 20 with a nut, thereby clamping an endof the tubular tether belt 11 a between those members. Further,respective ends of the connecting member 20 are clamped between thecushion ring 22 and the base plate 24 to be thereby secured to the baseplate 24. Further, as described in detail later, reference numeral 12′denotes a gas rectification member, and 11 c denotes a stitched partwhere the tubular tether belt 11 a is stitched to the airbag main body10 a.

Now, there are described hereinafter respective structures of the baseplate 24, the connecting member 20 and the cushion ring 22.

FIG. 3 is a perspective view showing the back side of the base plate 24shown in FIG. 2. The base plate 24 is formed substantially in the shapeof a disk, and an opening 24 h in which an inflator can be fitted isformed at the central part of the base plate 24, while 4 pieces ofairbag cover attachment pieces 24 a and a pair of attachment pieces 24 bfor attachment of the base plate 24 itself are formed in such a way asto be erected from the disk. The base plate 24 is for integrallysecuring the inflator 30, the airbag 10 and the previously describeddecorative member 40 with each other, and the pair of the attachmentpieces 24 b are for securing the base plate 24 to the steering wheel.

The inflator 30 is formed substantially in the shape of a thick disk andis made up so as to exhaust gas upon detection of a predeterminedimpact. The inflator 30 has an upper portion with a gas exhaust port 30a formed therein penetrating through the opening 24 h of the base plate24 and a flange formed substantially in an intermediate part of inflator30 in the direction of thickness thereof in close contact with the backside of the base plate 24, thereby being secured together with thecushion ring 22, to the base plate 24 through the attachment holes 24 cof the base plate 24. That is, the inflator 30 is secured to the baseplate 24 with the gas exhaust port 30 a of the inflator 30 disposed onthe front side of the base plate 24, so that an exhaust gas from theinflator 30 is exhausted on the front side of the base plate 24.

FIG. 4 is a perspective view of the connecting member 20 shown in FIG.2. The connecting member 20 is made of a metal piece in a sheet-likeshape, comprising a central part 20 a provided with a hole 20 ah inwhich the attachment bolt 40 a is fitted, a leg part 20 b formed on eachof both sides of the central part 20 a bent substantially verticallytherefrom, and attachment foots 20 c bent substantially right angles tothe respective leg parts 20 b. Further, each attachment foot 20 c isprovided with an attachment hole 20 e made so as to correspond to theattachment holes 22 a of the cushion ring 22 and the attachment holes 24c of the base plate 24, so that both connecting member 20 and the baseplate 24 are tightened up each other with bolts 22 d formed on thecushion ring 22.

FIG. 5A is a front elevation of the cushion ring 22 shown in FIG. 2, andFIG. 5B is a side view showing a part thereof, in section. As shown inFIG. 5A, the cushion ring 22 is substantially in the shape of arectangle, a central part thereof is provided with an insertion opening22 h for the inflator 30, and the bolt 22 d for attaching the cushionring 22 to the base plate 24 is provided in respective corners of thecushion ring 22 around the insertion opening 22 h on the back side ofthe cushion ring 22. Further, the back side of the cushion ring 22constitutes a butting surface 22 b that can be butted against thesurface of the base plate 24 through the airbag 10 interposedtherebetween, the butting surface 22 b has a depressed part 22 c formedby, for example, drawing work, as is evident from the side view of FIG.5B. The depressed part 22 c is formed so as to have a draw depthsubstantially equal to a thickness of the attachment foot 20 c of theconnecting member 20 when the cushion ring 22 is connected with theconnecting member 20.

Now, the airbag 10 is described hereinafter with reference to FIGS. 6A,and 6B.

FIG. 6A is a see-through perspective view showing the interior of theinflated airbag 10, and FIG. 6B is a perspective view showing theun-inflated airbag 10. For brevity, the decorative member 40 and soforth inside the tubular tether belt 11 a, the inflator 30 joined withthe decorative member 40 and so forth are not shown in those figures.

The airbag main body 10 a is formed in the shape of a bag that isexpandable into a flat spherical shape (an ellipsoidal shape) by joiningrespective outer circumferential edges of two pieces of clothsubstantially circular in shape with each other by stitching. A notchedpart 10 h of circular shape for insertion of the depressed part 16 a ofthe airbag cover 16 is formed substantially at the central part of theairbag main body 10 a on the front side thereof, and an inflatorattachment opening 10 ah associating with the inflator for introducingan generated gas into the airbag is formed substantially at the centralpart of the airbag main body 10 a on the back side thereof, while foursmall holes 10 b for insertion of the respective bolts 22 d (see FIG.5B) of the cushion ring 22 are made on the peripheral part 10 d aroundthe inflator attachment opening 10 ah.

The protective member 12 for protecting the airbag from heat and animpactive pressure generated by the inflator is overlaid on theperipheral part 10 d and stitched to a peripheral edge of the inflatorattachment opening 10 ah of the airbag 10. With the present embodiment,the protective member 12 is also used as a gas rectification memberhaving a function for guiding the gas up to the vicinity of a part ofthe airbag (a part of the airbag expanding from an anticipated rupturepart of the holding member 14 of circular shape) that will inflate inthe initial expansion thereof by rectifying a gas flow direction.

As shown in FIG. 6A, the protective member 12 is made of, for example, awoven cloth and is hollow at the center and formed in a concentriccircle, and a diameter of the hollow inner circumference thereof isidentical to that of the inner periphery of the inflator attachmentopening 10 ah, while an outer circumference thereof is for example atleast three times as large in diameter as the inner circumference. Whenattaching the protective member 12 to the inflator attachment opening 10ah, an inner peripheral edge of the protective member 12 is stitched toan outer circumferential part 10 d′ of the peripheral part 10 d inalignment with the peripheral edge of the inflator attachment opening 10ah and an outer circumferential part 12′ of a concentric circle of theperipheral part 10 d. The protective member 12 has the function forprotecting the airbag from heat and impact of gas pressure as well asthe function as the rectification member for rectifying gas after theairbag 10 is folded and contained. Further, one sheet of the protectivemember 12 is effective, however, two or more sheets thereof may beadopted, and maybe used for the gas rectification member.

The airbag 10 comprises the airbag main body 10 a and the tubular tetherbelt 11 a for restricting the extension length of the airbag main body10 a, the airbag main body 10 a is provided with a stitched part 10 cformed by stitching respective outer peripheral edges of two pieces ofbase fabrics (a base fabric of the surface portion of the airbag mainbody and a base fabric of the rear surface portion thereof)substantially circular in shape with each other, and an airbag afterstitched is turned inside out, thereby forming the airbag main body inthe shape of the bag expandable into the flat spherical shape (theellipsoidal shape).

As is evident from FIG. 6B, the two pieces of the base fabricssubstantially circular in shape are substantially identical in size toeach other. The airbag 10 after stretched substantially to a full lengthin the direction of extension of the thereof as shown in FIG. 6A (upperpart of the figure) is folded like bellows and vertically compressed tobe contained in the airbag cover 16. At the same time, not only theairbag main body 10 a but also the tubular tether belt 11 a is foldedlike bellows in the direction of a tube length thereof. The tubulartether belt 1 a when stretched substantially to the full length thereofhas a length substantially equal to a length of the front and back basefabric of the airbag main body 10 a respectively.

Now, there is described hereinafter a method of folding like bellows theairbag 10 stretched substantially to the full length thereof in thedirection of the extension of the airbag as shown in FIG. 6A (upper partof the figure) to be vertically compressed. For the method of foldinglike bellows the airbag 10, an airbag-folding machine may be used. FIGS.7A to 7H are schematic views showing operating process for folding theairbag with the airbag-folding machine. The operating process forfolding the airbag will be described hereinafter with reference to thoseschematic views.

As shown in FIG. 7A, the airbag-folding machine 60 comprises a table 61having a support member 62 columnar in shape for supporting the tubulartether belt 11 a and an outer cylinder 63 coaxial with the supportmember 62 for containing the airbag 10 on the outside of the supportmember 62, and a support unit (not shown) for supporting a clampingmember 64 columnar in shape (see FIG. 7C), positioned vertically abovethe support member 62 and substantially identical in outer diameterthereto, to thereby clamp the upper end of the tubular tether belt 11 abetween a clamping member 64 and the support member 62. Since the outerdiameter of the support member 62 is smaller than the inside diameter ofthe insertion opening 22 h of the cushion ring 22, the support member 62can be inserted through the insertion opening 22 h to thereby ascend asdescribed later.

Further, as shown in FIG. 7A, the bolts 22 d of the cushion ring 22 areinserted into the four small holes 10 b provided on the peripheral part10 d (see FIG. 6A) of the airbag 10 respectively, and the bolts 22 d areengaged with four holes provided on the periphery of the support member62 of the table 61 on the upper end thereof to be secured to the fourholes. The head of the support member 62 is inserted through theinsertion opening 22 h to thereby be ascended and inserted into a tubeportion of the tubular tether belt 11 a, and the airbag main body 10 ais placed flat on the top of the table 61 outside of the ascendedsupport member 62.

When a lower end of the tubular tether belt 11 a is pushed up with thehead of the support member 62 inserted into the tube portion of thetubular tether belt 11 a through the insertion opening 22 h of thecushion ring 22 as shown in FIG. 7A, the airbag main body 10 a is alsopushed up as shown in FIG. 7B.

As described in the foregoing, since the length of the tubular tetherbelt 11 a is substantially equal to half the length of the airbag mainbody 10 a, the support member 62 ascends to a position at a height atthe maximum about three times of the length of the tubular tether belt11 a and stops at the position, whereupon the tubular tether belt ismanually passed through a protrusion provided at the tip of the supportmember 62 through the attachment hole 11 ah, thereby implementingpositioning of the tubular tether belt 11 a.

As shown in FIG. 7C, the clamping member 64 descends to clamp saidpositioned tubular tether belt 11 a between the support member 62 andthe clamping member 64, the support member 62 and the clamping member 64descend with the tubular tether belt 11 a being kept in clampedposition.

As shown in FIG. 7D, upon the support member 62 and the clamping member64 descending to a position corresponding to half the length of thetubular tether belt 11 a, descending operation is stopped, then theairbag main body 10 a placed on the outside is manually pulled up asshown in FIG. 7D. By so doing, the tubular tether belt 11 a is foldedsubstantially at an intermediate position thereof.

As shown in FIG. 7E, the outer cylinder 63 ascends from the table 61 upto a clamping position of the upper end of the tubular tether belt 11 a,thereby containing the airbag 10 between the outer cylinder 63 and thesupport member 62. As shown in FIG. 7F, with the outer cylinder 63 atthat position, two pieces of plates 65, each having a hole bilaterallysymmetric and semi-circular in shape, are caused to slide on an upperend of the outer cylinder 63 from the right side and the left sidethereof respectively, to be fitted into a fitting groove (not shown)provided at a lower end of the clamping member 64.

Then, as shown in FIG. 7G, the support member 62, the clamping member 64and the outer cylinder 63 in keeping that position are caused toconcurrently descend, whereupon the folded tubular tether belt 11 aoverlaid together with the airbag main body 10 a will be folded likebellows while being compressed. Upon completion of compression of theairbag 10 (see FIG. 7H), the plates 65 are removed, and subsequently thesupport member 62, the clamping member 64 and the outer cylinder 63concurrently revert to respective original positions, thereby completingthe operation for folding the airbag 10.

Meanwhile, the length of the airbag 10 has been described in theforegoing as the length of the tubular tether belt 11 a is substantiallyequal to half the length of the airbag main body 10 a when the airbag 10is stretched to the full length thereof, however, it is to be pointedout that the invention is not limited to the length described, and thatthe respective positions where the support member 62 and the clampingmember 64 stop after descending as well as the position where thesupport member 62 stops may be decided depending on a length of theairbag 10.

FIG. 8A is an expansion view of the holding member 14 prior to coveringthe airbag 10. The holding member 14 in the shape of an approximatesquare is made of a woven cloth, and an opening 14 h substantiallycircular in shape is provided at the center thereof while eight holes 14ah, 14 bh, to be engaged with the bolts 22 d of the cushion ring 22respectively, are provided at the respective centers of four sides ofthe approximate square, and at respective corners of the approximatesquare along respective diagonal lines thereof respectively. The opening14 h substantially circular in shape has a shape and size which issufficient to allow respective diameters of the depressed part 16 a ofthe airbag cover 16, and the decorative member 40 to pass through theopening 14 h.

FIG. 8B is a perspective view showing the back side of the holdingmember 14 prior to covering the airbag 10 and the back side of theairbag 10 as folded by the airbag-folding machine 60 previouslydescribed. The four pieces of the holes 14 ah are engaged with the bolts22 d of the cushion ring 22, protruding from the airbag 10 as foldedrespectively. Thereafter, the holes 14 bh positioned on the respectivediagonal lines are all engaged with the opposite bolts 22 d.

FIG. 8C is a perspective view showing the folded airbag 10 covered withthe holding member 14. When covering the airbag 10 by the holding member14, the airbag 10 is covered by the holding member 14 with theattachment hole 11 ah of the tubular tether belt 11 a shown in FIG. 6A,to overlie the attachment bolt insertion hole 14 hh of the holdingmember 14.

FIG. 8D is a backside view of the airbag 10 covered with the holdingmember 14. As the protective member 12 is folded like bellows inside theairbag 10, the same is pulled out to be thereby disposed along the innerperiphery of the airbag 10 folded as shown in FIG. 8D (or FIG. 2). By sodoing, the protective member 12 carries out the function as the gasrectification member. Apart of the protective member 12, which is oncepulled out to be thereby disposed along the inner periphery of thefolded airbag 10 shown in FIG. 8D (or FIG. 2) is hereinafter referred toas a gas rectification member 12′. Further, by covering the airbag 10with the holding member 14, the attachment hole 11 ah of the tubulartether belt 11 a overlying the attachment bolt insertion hole 14 hh isdisposed substantially at the center of the inflator attachment opening10 ah of the airbag 10, in other words, substantially at the center ofthe gas rectification member 12′ which is formed to reach the vicinityof the part of the airbag inflating in the initial expansion thereof.The gas rectification member 12′ is attached to the foregoing inflatorattachment opening 10 ah when held by the holding member 14 as shown inFIG. 8D, and has a surface with multiple-folded pleats 12 a formedthereon.

Meanwhile, with the airbag 10 held by the holding member 14, whencontained in the airbag cover 16, the gas rectification member 12′ isextended along the inner wall of the airbag 10 toward the front sidefrom the cushion ring 22 clamping the inflator attachment opening 10 ahof the airbag 10 up to the vicinity of the tip of the folded tubulartether belt 11 a, the part of the airbag that will inflate in theinitial expansion thereof, as shown in FIG. 2. The gas rectificationmember 12′ in this state is tubular in shape. Since the multiple-foldedpleats 12 a are formed on the surface of the gas rectification member12′ to thereby have great effect as the protective member for protectingthe periphery of the inflator attachment opening 10 ah of the airbag 10from heat and impact of gas pressure and also have a function as therectification member for rectifying the gas since the protective member12 is tubular in shape.

The bolts 22 d of the cushion ring 22 inserted when folding the airbag10 are shown as protruded from around the peripheral edge of theinflator attachment part, on the backside of the airbag 10. As a resultof covering the airbag 10 with the holding member 14, a side face of theairbag 10, on the outer circumference thereof, is pressed down, so thatit is possible to restrain the inflation and expansion of the airbag 10in the direction of the side face thereof, caused by the gas generatedfrom the inflator in the initial expansion of the airbag 10.

If the protective member 12 is made of a woven cloth as in the case ofthe airbag 10, the protective member 12 is formed by overlaying cloth ofa predetermined width on the peripheral part 10 d around the inflatorattachment opening 10 ah to be thereby stitched therewith. Theprotective member 12 needs to have a length reaching the vicinity of thepart of the airbag 10 that will inflate in the initial expansionthereof, preferably a length reaching, for example, the tip of thefolded tubular tether belt 11 a.

For a material of the protective member 12, material other than amaterial of the airbag 10, for example, a synthetic resin sheet, and anyflexible material capable of carrying out the function for rectifyinggas can be used. In such a case, it need only be sufficient to securelystick the airbag 10 and the synthetic resin sheet together byappropriate means. Further, it is also possible to carry out theinvention with the protective member 12 made as a separate memberwithout securely sticking to the airbag 10. If the protective member 12is the separate member, the protective member 12 is not limited to thesynthetic resin sheet, and may be one made of metal. In such a case, itneed only be sufficient to rectify the gas generated from the inflatorto flow only toward the part of the airbag that will inflate in theinitial expansion thereof. The protective member 12 may be eitherintegrally joined with the bolts 22 d of the cushion ring 22, or may beattached as a member completely separated therefrom. Otherwise, theprotective member 12 may be welded to the base plate 24, or may beformed by deep drawing.

If the protective member 12 is made of a woven cloth as in the case ofthe airbag 10, it need only be sufficient to dispose cylindrically theprotective member 12 prepared by overlaying cloth of a predeterminedwidth on the peripheral part 10 d around the inflator attachment opening10 ah to be thereby stitched therewith. The protective member 12 needsto have a length reaching the vicinity of the part of the airbag 10 thatwill inflate in the initial expansion thereof, preferably a lengthreaching, for example, the tip of the folded tubular tether belt 11 a.

FIG. 9A is a perspective view of the airbag cover 16. The airbag cover16 is formed of a synthetic resin so as to be substantially in abowl-like shape, and the depressed part 16 a for accommodating thedecorative member 40 is provided at the central part of the airbag cover16, as previously described. The airbag cover 16 is secured to the baseplate 24 with rivets through the intermediary of the airbag coverattachment pieces 24 a. Further, with the decorative member 40 attachedto the depressed part 16 a of the airbag cover 16, a surface of thedecorative member 40 is substantially flush with a surface of the airbagcover 16, as shown in FIG. 2.

FIG. 9B is a back side view of the airbag cover 16. As shown in thefigure, tear-lines (L1 to L4, Lc) in a groove-like shape, capable ofsplitting and tearing upon the inflation and expansion of the airbag 10,while leaving out the depressed part 16 a at the center secured by theconnecting member 20, are formed on the back side of the airbag cover16. More specifically, the back side of the airbag cover 16 is providedwith a series of the tear-lines comprising the tear-line Lc circular inshape, formed around the depressed part 16 a, and a plurality of thetear-lines, for example, four pieces of the tear-lines L1 to L4,radially extended from the tear-line Lc, so as to enable the airbagcover 16 to be split into a plurality of cover pieces 16 b with thedepressed part 16 a left out as it is, upon the airbag cover 16 beingsubjected to an inflation pressure of the airbag. Further, the airbagcover 16 is secured to the base plate 24 with the rivets such that theairbag cover 16 can be split into the respective cover pieces 16 b uponthe inflation of the airbag 10, and the respective cover pieces 16 b canindependently open up.

With the above structure, when the inflator 30 is actuated and theairbag 10 undergoes inflation and expansion by a gas pressure, theairbag cover 16 is pressed to be split along the respective tear-lines Laround the decorative member 40 by a force of the inflation andexpansion, whereupon the split cover pieces will open outwardrespectively, with the depressed part 16 a in the bowl-like shape at thecenter being left out as it is, to be then completely cut apart andindependently open up respectively, as described above.

FIG 10 is a view showing the respective opened-up cover pieces 16 b, asseen from an occupant side. As shown in the figure, because the airbagcover 16 is split into the respective cover pieces 16 b upon theexpansion of the airbag 10, the airbag cover 16 will not interfere withthe expansion of the airbag 10 in the direction of the side facethereof, after the airbag 10 passes through the anticipated rupture part14 h of the holding member 14. For brevity, the airbag and so forth arenot shown in the figure.

Herein, there is described a process for assembling the airbag device M1with reference to FIGS. 3 to 5, and FIGS. 8 and 10.

On assembling, the airbag 10 with the cushion ring 22 pre-containedtherein and packaged in the holding member 14 is contained in the airbagcover 16 by aligning the position of a hole 16 ah of the airbag cover 16with that of the tubular tether belt attachment hole 11 ah of the airbag10. Then, while the connecting member 20 is inserted into the airbag 10such that a position of the hole 20 ah of the central part of theconnecting member 20 is aligned with that of the tubular tether beltattachment hole 11 ah, the bolt 22 d protruding from the depressed part22 c of the cushion ring 22 into the airbag 10, as shown in FIG. 8D, isinserted into the attachment hole 20 e of the connecting member 20,thereby fitting the attachment foot 20 c into the depressed part 22 c.

By inserting the attachment bolt 40 a of the decorative member 40 intothe hole 16 ah of the depressed part 16 a of the airbag cover 16 fromthe front side, it is possible to insert the attachment bolt 40 a intothe hole 16 ah of the airbag cover 16, the attachment hole 11 ah of thetubular tether belt 11 a of the airbag 10 and the hole 20 ah of thecentral part of the connecting member 20 disposed in alignment with thehole 16 ah respectively. By screwing down a nut against the attachmentbolt 40 a, the attachment bolt insertion hole 14 hh and the attachmenthole 11 ah of the tubular tether belt 11 a are clamped and securedbetween the depressed part 16 a of the airbag cover 16 and the centralpart 20 a of the connecting member 20.

Then, by inserting the bolts 22 d of the cushion ring 22 into theattachment holes 24 c of the base plate 24 respectively, the cushionring 22 is overlaid on the base plate 24 to thereby fit the base plate24 to the airbag cover 16, and further the inflator 30 is snapped inbetween the bolts 22 d, thereby screwing down a nut against therespective bolts 22 d. By so doing, the inflator attachment opening 10ah and the protective member 12 are clamped and secured between thecushion ring 22, and the connecting member 20. As a result, assemblingof the airbag device M1 shown in FIG. 2 is completed.

Referring to FIGS. 11A and 11B, there is described hereinafter anexpanding action of the airbag device M1.

First, upon detection of an impact due to vehicle collision and soforth, ignition starts in the inflator 30 to thereby cause gas to begenerated therein, and the gas is introduced into the airbag 10. Whenthe airbag 10 starts inflation, the airbag cover 16 is subjected to aforce of the inflation and is split along the tear-lines L1 to L4, andLc, that is, with depressed part 16 a as left out as it is, whereuponthe respective cover pieces 16 b will radially expand.

In the initial stage in which the gas is introduced into the airbag 10and the airbag 10 starts to be inflated after the airbag cover 16 issplit, as shown in FIG. 11A, inflation and expansion start from thestitched part 11 c formed by stitching together the tubular tether belt11 a and the central part of the base fabric of the airbag 10 that willstart inflation in the initial expansion, while enveloping the depressedpart 16 a with the tubular tether belt 11 a, and the surface of theairbag 10 undergoes inflation toward the occupant side.

Since the tubular tether belt 11 a is folded in the longitudinaldirection of the tube portion at the time of the inflation, the tubulartether belt 11 a is hardly subjected to resistance upon extensionthereof. When the airbag 10 undergoes inflation and expansion from thestitched part 11 c, the airbag 10 undergoes expansion toward theoccupant side while subjected to resistance upon passing through theanticipated rupture part 14 h of the holding member 14. Accordingly,surface portion of the airbag 10 will sequentially be expanded towardthe occupant side, while maintaining a degree of an internal pressurewithout causing halfway collapse of folded and contained airbag 10.

Meanwhile, FIG. 11A shows the fully stretched tubular tether belt 11 ato its full length. Parts of the back side portion of the airbag 10 areinflated and expanded toward the occupant side, but the stitched part 10c formed by stitching together the respective outer circumferentialedges of the two pieces of the base fabrics substantially circular inshape is positioned in the vicinity of the steering wheel 50, and otherparts of the back side portion of the airbag 10 are still contained inthe holding member 14. After the airbag has inflated to a degree, theposition of the stitched part 10 c shifts from the right-hand part ofthe figure toward the left as far as substantially the center along thecenter line of the tubular tether belt 11 a, whereupon the airbag 10 isturned into the flat spherical shape, as shown in FIG. 11B, therebycompleting the inflation and expansion. Reference numeral 12′ denotesthe gas rectification member.

The airbag 10 exhibits a behavior whereby expansion thereof toward theoccupant side is stopped following the tubular tether belt 11 astretching to its full length as described above, this behavior is tostop the rapid stretch of the tubular tether belt 11 a due to theinternal pressure immediately after splitting and to temporarilyincrease an internal pressure of the airbag inside the airbag cover 16to obtain a splitting and tearing force, and in association with suchstopping action, the airbag 10 is stretched, however, since a volume ofthe airbag 10 rapidly increases concurrently with expansion thereof, theinternal pressure rapidly decreases. Whereas the airbag 10 itself tendsto stretch by an inertial force thereof, however, the expansion of theairbag 10 toward the occupant side is stopped before the internalpressure sufficiently increases due to stoppage of the stretching of thetubular tether belt 11 a and resistance by the holding member 14.

With the first embodiment of the invention, an expansion velocity towardthe occupant side after the stopping action is actually decreased byhalf as compared with a stretch velocity of the remaining parts of theairbag 10 within the holding member 14, since the central part of theairbag 10 cannot shift toward the occupant side, harmfulness againstoccupants will decrease as compared with the case of an airbag devicewithout the tubular tether belt 11 a.

Such an advantageous effect as above is not limited to the case of thetubular tether belt 11 a according to the first embodiment, and the sameeffect is obtained in the case where a usual flat tubular tether belt isprovided.

FIGS. 12A to 12D are views showing the expanding airbag 10 of the airbagdevice M1 according to the first embodiment. FIGS. 12A to 12D show theexpanding airbag at the same timing in order to compare with theexpanding airbag 10 of the prior art.

At the timing in FIG. 12A, it is found that the shape of the inflatingand expanding airbag 10 undergoes inflation and expansion only at itssurface portion and each volume of upper and lower portions of theairbag 10 is substantially the same, and the airbag 10 bursts out in astate where the position of the stitching part 10 c formed by stitchingouter circumferential edges of two pieces of cloth substantiallycircular in shape is positioned in the vicinity of the steering wheel50. In other words, in the initial stage of inflation and expansion ofthe airbag 10, the airbag 10 undergoes inflation and expansionsubstantially concentrically in the order of being folded from thestitching part 11 c which is formed by stitching the central part of thefabric and the tubular tether belt 11 a.

At the timing in FIG. 12B, it is found that only the front side of theairbag 10 undergoes inflation and expansion toward the occupant side andcircumferential side, while parts of the upper and lower portions of theairbag 10 at the back portion undergo inflation and expansion not towardthe occupant side but toward the back side of the steering device, andthe airbag 10 undergoes inflation and expansion in a state where theposition of the stitching part 10 c remains in the vicinity of thesteering device in the same manner as the case of FIG. 12A. At thetiming in FIG. 12C, it is found that the front side of the airbag 10further undergoes inflation and expansion toward the occupant side andcircumferential side compared with the state in FIG. 12B, and the partsof the upper and lower portions of the airbag 10 at the backward portioncontinue to further undergo inflation and expansion toward the back sideof the steering device, while the airbag 10 undergoes inflation andexpansion with the stitching part 10 c still remaining in the vicinityof the steering device in the same manner as shown in FIG. 12B. At thetiming in FIG. 12D, it is found that the position of the stitching part10 c moves from the portion in the vicinity of the steering device tothe occupant side, and the backward portion of the airbag 10 undergoesinflation and expansion toward the occupant side.

Comparing the expanding state of the airbag 10 according to the firstembodiment with that of the conventional airbag device, at the timing inFIG. 20B showing the conventional airbag device, since the lump of theairbag 10 bursts out under the chin of the dummy, then at the timing inFIG. 20C, airbag covers from the chin to the cheek ,while at the timingin FIG. 20D, the face of the dummy is covered with the airbag, it isassumed that the inner pressure quickly increases around the lowerperiphery of the chin to cause the membrane phenomenon to occur.

On the other hand, it is evident that at the timing in FIG. 12B of thefirst embodiment, only the front portion of the airbag 10 undergoesinflation and expansion toward the occupant side and circumferentialside so that the front portion of the airbag 10 directly contacts theoccupant, thereafter at the timing in FIG. 12C, only the front portionof the airbag 10 contacts the head of the passenger even in the casewhere the front portion of the airbag 10 still further undergoesinflation and expansion toward the occupant side and circumferentialside, thereby preventing the occurrence of the membrane phenomenon.Further, the expanding states of the airbag 10 in FIGS. 12A to 12D showthat the airbag undergoes expansion sequentially and orderly startingfrom a region where the expansion ought to be started. Accordingly, theairbag device M1 according to the first embodiment does not cause themembrane phenomenon to occur in a state where the stitching part 10 ccorresponding to the maximum diameter of the airbag 10 hang on the neck.

Subsequently, there is described hereinafter an airbag device M2 for afront passenger seat according to a second embodiment of the invention.As shown in FIG. 13, the airbag device M2 comprises an folded airbag 10A, an inflator 30A for feeding a gas for inflation to the airbag 10A, andan airbag cover 16A in the shape of an approximately square cylinder forcontaining the airbag 10A, and the inflator 30A therein. The airbagdevice M2 is substantially the same in structure as the airbag deviceM1, and in describing the structure of the airbag device M2, likeelements are given like reference numerals with “A” suffixed.

The airbag cover 16A is made up such that a tear-line LA disposed in theshape resembling the letter H is provided on the back side of the headin the shape of the approximately square cylinder in such a way as toenable the airbag cover 16A to be split into two pieces of cover pieces16Ab to open, and the two pieces of the cover pieces 16Ab can opentoward an upper side and a lower side respectively, as seen from theplane of the figure, with an upper edge and a lower edge of therespective cover pieces 16Ab, each serving as a hinge 16Ae. Further, aconnecting wall unit 16Af in the shape of an approximately squarecylinder protruding downward is provided on the back side of the head inthe shape of the approximately square cylinder in such a way as tosurround respective positions where the two pieces of the cover pieces16Ab are to be disposed.

A plurality of stopper holes 16Ag are penetrated through respectivepredetermined positions of upper and lower walls of the connecting wallunit 16Af, opposed to each other. Stopper fingers 24Ad formed on a baseplate 24A are inserted into the stopper holes 16Ag respectively, therebyengaging the stopper fingers 24Ad with the connecting wall unit 16Af.The respective stopper fingers 24Ad are secured to the connecting wallunit 16Af in order to ensure connection of the connecting wall unit 16Afwith the base plate 24A so that the airbag 10A at the time of inflationcan smoothly push up the two pieces of the cover pieces 16Ab to therebyenable the tear-line LA to be ruptured.

As shown in FIG. 13, the base plate 24A comprises abottom wall part 24Aein the shape of a rectangular sheet, formed of a sheet metalsubstantially rectangular in shape, having a rectangular opening, on theupper end side thereof, and a sidewall part 24Af extending so as to bein the shape of an approximately square cylinder from the outerperipheral edge of the bottom wall part 24Ae upward toward the airbagcover 16A. The bottom wall part 24Ae is formed in the shape of arectangular sheet extended longer from side to side, and the centralpart thereof is provided with an inflator attachment opening 24Ahcircular in shape, through which an upper side part of an inflator 30Acan be inserted from below the bottom wall part 24Ae upward toward theairbag cover 16A.

As shown in FIG. 14, attachment holes 22Ag through which respectivebolts 22Ad of a cushion ring 22A can be inserted are formed on theperipheral edge of the inflator attachment opening 24Ah of the bottomwall part 24Ae. Further, as shown in FIG. 13, a bracket 32 forconnecting the base plate 24A on the side of a vehicle body 60 a issecured to the respective undersides of both the right and left side ofthe bottom wall part 24Ae. A nut for screwing a bolt into each of therespective brackets 32 is securely attached thereto. A bracket 60 bextending from a reinforcement 60 a is provided on the side of theairbag device M2, adjacent to the vehicle body 60, and a bolt ispenetrated through an attachment seat of the bracket 60 b to be screwedwith a nut. By tightening up the nuts against the bolts, respectively,the airbag device M2 is attached to, and secured to the body 60.

Next, there is described a procedure for assembling the airbag device M2with reference to FIGS. 13 and 14.

FIG. 14 is an enlarged view showing a gas rectification member 12A′, theairbag 10A and a holding member 14A. As is the case with the airbag 10of the airbag device M1, except for the tubular tether belt 11 a, thefolded airbag 10A for use in the airbag device M2, incorporating thecushion ring 22A, described with reference to FIGS. 8A to 8D, is coveredwith the holding member 14A. The airbag 10 covered with the holdingmember 14A is contained in the airbag cover 16A, and the inflatorattachment opening 24Ah of the base plate 24A is fitted onto the bolts22Ad of the cushion ring 22A to thereby overlay the base plate 24A onthe cushion ring 22A while the stopper fingers 24Ad of the base plate24A are inserted into the stopper holes 16Ag of the airbag cover 16Arespectively, to be secured thereto, thereby screwing nuts from thebackside of the base plate 24A.

Thereafter, the base plate 24A, the cushion ring 22A and the inflator30A are screwed together. By so doing, the gas rectification member12A′, the airbag 10A and a holding member 14A are clamped and securedbetween the cushion ring 22A and the base plate 24A, thereby completingassembling of the airbag device M2. Further, the shape of the airbagcover 16A of the airbag device M2 is not limited to that described asabove, and decision on what shape is to be adopted for the airbag cover16A can be made according to a design depending on an installation placeof the airbag device M2, including, for example, the upper face of aninstrument panel and so forth.

Further, since the airbag device M2 is not provided with the tether beltcompared with the case of the airbag device M1, an expansion action ofthe airbag device M2 does not exhibit the behavior whereby expansionthereof toward the occupant side is temporarily stopped, and the airbag10A undergoes inflation and expansion toward an occupant side whileinflating from a portion thereof facing the occupant side with aninternal pressure of the airbag maintained to a degree. Thus, becausethe airbag undergoes orderly inflation starting from the surface thereofon the occupant side by virtue of the gas rectification member 12A′,even without the tether belt, and expands toward the occupant side afterbeing subjected to resistance while passing through an opening of theholding member 14A, there will not occur a behavior whereby the airbagin whole bursts out in a lump concurrently with splitting and tearing ofthe airbag as folded, thereby inflicting harm on an occupant, so thatoccurrences of a punching phenomenon and a membrane phenomenon can beprevented with reliability.

Subsequently, there is described hereinafter an airbag device M3 for afront passenger seat according to a third embodiment of the invention.The airbag device M3 shown in FIG. 15 is substantially the same instructure as the airbag devices M1, M2, respectively, and members of theairbag device M3, identical to those of the airbag devices M1, M2,respectively, are denoted by like reference numerals with “B”suffixed.FIG. 15 is a schematic enlarged longitudinal sectional view of theairbag device M3 for the front passenger seat. The airbag device M3comprises an folded airbag 10B, an inflator 30B substantially columnarin shape, contained in the airbag 10B, for feeding a gas for inflation,a diffuser 32B for containing the inflator 30B therein, and an airbagcover 16B in the shape of an approximately square cylinder, forcontaining the airbag 10B, and the inflator 30B therein.

The airbag cover 16B is provided with a tear-line LB disposed in theshape resembling the letter H on the back side of a head part of theapproximately square cylinder to enable the airbag cover 16B to be splitinto two pieces of cover pieces 16Bb to open, and the two pieces of thecover pieces 16Bb can open toward an upper and a lower side as seen fromthe plane of the figure respectively, by making use of an upper and alower edge of the respective cover pieces 16Bb as a hinge 16Ae.

Further, a connecting wall unit 16Bf in the shape of an approximatelysquare cylinder, protruding downward is provided on the back side of thehead part of the approximately square cylinder in such a way as tosurround respective positions where the two pieces of the cover pieces16Bb are to be disposed.

The diffuser 32B is secured to the airbag cover 16B by inserting bolts(not shown) into the respective holes provided at a plurality of fixturepositions of both members 32B and 16B and securing them.

The diffuser 32B is disposed between the inflator 30B and the folded andcontained airbag 10B and is provided with a plurality of gas exhaustholes (not shown) through which a gas for inflation can flow out, sothat the airbag device M3 is structured such that upon actuation of theinflator 30B, a gas generated from the inflator 30B passes through thegas exhaust holes of the diffuser 32B to thereby apply pressure to thecentral part of the folded and contained airbag 10B.

Reference numeral 11B denotes a usual tether belt unlike the tubulartether belt as previously described, and reference numeral 12B′ denotesa gas rectification member. Both the members 11B, 12B′ together with theairbag 10B overlapped one another are inserted between the respectivemembers 32B and 16B on fixedly attaching the diffuser 32B to the airbagcover 16B, and the respective members 11B, 12B are secured with bolts tobe thereby being attached to the airbag device. Further, as is evidentfrom FIG. 15, with the airbag device M3 employing the inflator 30B ofthe type described, the airbag 10B is not provided with the inflatorattachment opening 10 ah, but is provided with a communicating port forinsertion of the inflator 30B, and the inflator 30B is inserted into thecommunicating port. Further, an airbag device wherein a gas from aninflator of an airbag device (not shown) into an airbag through acommunicating port thereof from outside the airbag instead of insertingthe inflator directly into the airbag is well known in the art.

Accordingly, the respective inflator attachment openings 10 ah of theairbag 10,10A used in the airbag devices M1, M2, respectively, thecommunicating port for insertion of the inflator 30B and thecommunicating port of the well known airbag have the same function asthe communicating port for introducing the gas from the inflator intothe airbag, therefore, when the word of communicating port of theinflator is used, it will be understood that it means the inflatorattachment opening, the communicating port for insertion of the inflatorand the communicating port of the well known airbag as well.

Thus, as is evident from the respective structures of the airbag devicesM1, M2, and M3, shown in FIGS. 2, 13, and 15, respectively, in theinitial stage when the gas is exhausted from the respective inflators30, 30A and 30B, the gas generated from the respective exhaust ports 30a, 30Aa and 30Ba of the inflators 30, 30A, and 30B are rectified by therespective gas rectification members 12′, 12A′, and 12B′, to be guidedup to the vicinity of the part of the airbag, inflating in the initialexpansion thereof, and concurrently, the holding member 14 prevents theairbag 10 from inflating in the direction of both the sides thereof, sothat the respective airbags 10, 10A, 10B undergo sequential and orderlyexpansion starting from a region where the expansion ought to bestarted, thereby preventing a punching phenomenon whereby the airbagpartially bursts out in a lump toward the occupant side.

If the respective folded airbags 10, 10A, 10B are disposed on respectiveouter peripheries of the protective members 12, 12A, 12B at this pointin time, this will cause the respective folded airbags 10, 10A, 10B, tobe compressed by a gas pressure of each of the inflators 30, 30A, 30Bbetween the respective gas rectification member 12′, 12A′, 12B′ and theholding member, so that the respective airbags 10, 10A, 10B can befirmly maintained in its contained state by a resultant compressionforce, and it is possible to prevent successfully occurrence of thepunching phenomenon in which the airbag partially bursts out in the lumptoward the occupant side as a result of collapse in the folded-states ofthe respective airbags 10, 10A, 10B, due to the impact given in theinitial expansion thereof.

Further, if the respective airbags 10, 10A, 10B, are disposed as abovedescribed, this will lead to formation of a structure in which a forceapplied to the gas rectification members 12′, 12A′, 12B′ respectivelycan be fended off with the respective airbags 10, 10A, 10B, so that thegas rectification members 12′, 12A′, 12B′ no longer require a particularstrength. Further, the protective member originally intended forprotection of only the peripheral part 10 d of the inflatorcommunicating port 10 ah can be used as the gas rectification members12′, 12A′, 12B′ and also as a protective member for protection of thewhole inner face of each of the airbags. Still further, since theprotective member spreads from the peripheral portion 10 d of theinflator communicating port 10 ah toward the outer circumference of theconcentric circles, when the protective member is disposed on the innercircumference side of each of the folded airbags 10, 10A, 10B, therespective protective members 12, 12A, 12B are actually multiple-foldedto thereby form pleats. As a result, with just one sheet of theprotective member, it is possible to obtain the same protection effectas is obtained with several sheets of the protective member, andfurther, the respective airbags 10, 10A, 10B, in whole, can be quiteefficiently protected.

With the first embodiment, the stitched part 10 c shown in FIG. 12Aformed by stitching respective outer circumferences of the fabric of thefront portion of the airbag 10 and the fabric of a lower portion thereofwith each other, is temporarily positioned in the vicinity of thesteering wheel 50 in the initial expansion of the airbag 10 undergoinginflation and expansion, and the stitched part 10 c does not shifttoward the driver seat side before rising of an internal pressure of theairbag. Accordingly, even in the OOP state in which an occupant is notseated at the normal seating position, the airbag undergoes inflationsuch that the surface of the airbag 10, on the occupant's side, comesinto contact with the occupant without fail, as shown in FIG. 12,thereby eliminating the risk of the occupant sustaining an injury due tothe membrane phenomenon occurring when the stitched part 10 c where theairbag 10 has the largest diameter will wrap around the neck of theoccupant. Furthermore, if the resistance given by the holding member,when the airbag 10 undergoes expansion, is further increased, the airbag10 is sequentially inflated starting from the occupant side into aspherical shape, so that the punching phenomenon will be furtherlessened. The same applies to the second and third embodiments,respectively.

The airbag device M1 according to the first embodiment is provided withthe tubular tether belt 11 a, however, even if a string-like tether beltis installed instead, the airbag device M1 can carry out the same actionand effect as those for the case where the tubular tether belt 11 a isinstalled. Further, if the folded and contained airbag 10 is held by theholding member 14 even without a tether belt, it is possible to lessenthe punching phenomenon while accelerating an expansion velocity of theairbag 10, toward the occupant side, and to cause the airbag 10 in wholeto undergo uniform inflation to be thereby inflated into a shape capableof quickly protecting the occupant.

Further, as adaptability to the airbag device M1 for the driver seat isdescribed with reference to the first embodiment, and adaptability tothe airbag device M2 for the front passenger seat is described withreference to the second and third embodiments respectively, theinvention is adaptable to the airbag devices for the driver seat, andthe front passenger seat, respectively. Further, installation of therespective airbag covers 16, 16A, 16B is not a prerequisite for theinvention, and with the invention, it is intended that the respectivefolded and contained airbags 10, 10A, 10B are orderly expanded byrestraining those airbags by the respective holding members 14, 14A,14B, regardless of whether or not the respective airbag covers 16, 16A,16B are installed.

With the first, second and third embodiments using the airbag covers 16,16A, 16B together with the holding members 14, 14A, 14B respectively, inorder to speed up the start of the expansion, it is effective to disposethe respective tear-lines L, LA, LB of the airbag covers 16, 16A, 16B,in such a way as to oppose respective initially expanding parts of theairbag covers 16, 16A, 16B. With the first embodiment, the airbag deviceusing a pyro-type inflator is described, however, the invention is notlimited thereto, and with the use of either a hybrid-type inflator or astored-type inflator, the same effect can be obtained. Further, the gasrectification member formed of the same fabric as the base fabric of theairbag is described, however, the invention is not limited thereto, andfor the gas rectification member, various constituent materialsincluding metal can be utilized.

1. An airbag device comprising: an inflator; an airbag communicatingwith the inflator for undergoing inflation by a gas generated from theinflator; and a holding member for holding the airbag in a state asfolded and contained therein, and pressing down the outercircumferential side of the airbag, to thereby restrain inflation andexpansion of the airbag in the direction of the side thereof, caused bythe gas generated from the inflator at least in the initial expansion ofthe airbag, wherein a gas rectification member for rectifying andguiding the gas generated from the inflator up to the vicinity of a partof the airbag, inflating in the initial expansion thereof, is providedsubstantially at the central part of the airbag; wherein the holdingmember has an opening facing to the part of the airbag that will beinflated in the initial expansion thereof, and the airbag undergoesinflation and expansion through the opening.
 2. The airbag deviceaccording to claim 1, wherein the airbag is folded and contained on aside of the outer circumference of the gas rectification member.
 3. Theairbag device according to claims 1 or 2, wherein the gas rectificationmember is tubular in shape, the airbag is provided with a communicatingport for communicating with the inflator, and the gas rectificationmember is extended from a peripheral edge of the communicating port upto the vicinity of the part of the airbag that will inflate in theinitial stage of the expansion thereof.
 4. The airbag device accordingto claims 1 or 2, wherein the gas rectification member is made of awoven cloth.
 5. The airbag device according to claims 1 or 2, whereinthe gas rectification member is disposed as a member having a functionfor protecting the airbag from heat of the inflator and an impactivepressure thereof.
 6. The airbag device according to claims 1 or 2,wherein the holding member is made of a woven cloth for containing theairbag covered thereby.
 7. The airbag device according to claims 1 or 2,wherein the holding member is contained in an airbag cover.
 8. Theairbag device according to claim 7, wherein tear-lines to be split andtorn upon generation of the gas in the inflator to thereby form anexpansion port of the airbag are provided on a back side of the airbagcover.
 9. The airbag device according to claims 1 or 2, wherein a tetherbelt for restraining an extension length of the airbag toward anoccupant side, is disposed in the airbag.